Electrochemistry of anodic fluorine gas evolution at carbon electrodes: Part III characterization of activated carbon anodes following onset of the ?anode effect?

Research and application of a high-performance fluorocarbon plate prepared via modified a high temperature mould pressing method

As an indispensable part of the production of electrolytic fluorine, the quality of the carbon plate determines the running conditions and technical and economic indexes of electrolytic cells. Therefore, improving the service life of carbon plates has become an urgent challenge. Herein, special fluorocarbon plates were successfully prepared via direct heating and asphalt impregnation based on the resistance of the carbon plates, which not only improved their performance index, but also greatly reduced the cost of their production. According to electron microscopy (SEM) observation, the carbon plate prepared by the hot pressing method possessed a more compact internal structure and dislocation phenomenon, which reduced the contact pores between particles, increased the density and reduced the resistivity. The prepared carbon plate exhibited a density of 1.81 g cm^-3, resistivity of 25.8 µΩ m, and service life of 151 days. These results are superior to that of industrial carbon plates with a density of 1.74 g m^-3, resistivity of 36.7 µΩ m, and run time of 90 days, where our fabricated carbon plate exhibited an improvement of 4.5%, 29.7%, and 67.7%, respectively.

Unusual kinetic behavior in cathodic H2 evolution from KF.2HF melts at mild-steel and alloy electrodes

Apart from its interest as a "model" process for kinetic studies of gas-evolving electrode reactions, the cathodic hydrogen evolution reaction (her) is involved in several processes that are of importance in applied electrochemistry, e.g., as the cathodic co-reactions in the commercial production of C12 and F2, in electrolyses for production of hydrogen, in electrochemical hydrogenation and, indirectly, as the partial process in corrosion of base metals in the absence of oxygen. The present paper reports several aspects of the unusual behavior of the her that is involved as the co-reaction to electrolytic production of F2 from KF/HF melts using carbon anodes and Fe or mild-steel cathodes. Anomalous anodic polarization behavior that arises in electrolytic generation of F2 from KF/HF melts at carbon electrodes is well known. It is characterized by very high Tafel slopes associated with "CF" film formation and by sluggish F2 bubble disengagement from the electrode. Interest in such effects has, however, tended to overshadow rather similar, so-called "hyper polarization" effects that also arise in the cathodic reaction, but for different reasons. The origins and nature of such effects are described and characterized in the present paper, and comparisons are made between behavior of Hz evolution from KF.2HF and that from the aquo-system analogue, KOH.2H2O. An important aspect is the very different interfacial behavior in KF/HF or KF.2HF melts from that in the corresponding aquo-system. Effects of As-species in HF feeds is investigated in terms of electro catalysis and poisoning effects on the her.